Several approaches have been utilized for imparting soil resistance to carpets. One approach involves coating the carpet fibers with particulate inorganic oxides, such as silica. The improvement in soil resistance attained by this method is believed to be due, in part, to the oleophobic surface that the oxide coating presents to potential carpet contaminants. U.S. Pat. No. 2,622,307 (Cogovan et al.), U.S. Pat. No. 2,734,835 (Florio et al.), U.S. Pat. No. 2,786,787 (Florio), U.S. Pat. No. 2,928,754 (Schappel), U.S. Pat. No. 2,983,625 (Schappel), U.S. Pat. No. 2,987,754 (Schappel), U.S. Pat. No. 3,033,699 (Aarons), U.S. Pat. No. 3,671,292 (Hirshfeld et al.), U.S. Pat. No. 3,901,992 (Payne et al.) and U.S. Pat. No. 3,912,841 (Payne et al.) exemplify this technology.
However, many problems have been encountered with use of inorganic oxides on carpets. Such materials tend to adhere poorly to the surface carpet fibers, gradually becoming dislodged over time as the carpet wears or is repeatedly vacuumed or cleaned. This results in a discernible loss in soil resistance of the carpet. Furthermore, the dislodged particles tend to form a fine dusting on the surface of the carpet, thereby detracting from the vibrancy and aesthetic appeal of the carpet.
Many attempts have been made to prevent the disassociation of inorganic oxide particles from carpet fibers. Typically, this is accomplished by coating the treated carpet fibers with a binding agent. The binding agent is usually a material that bonds well to both the inorganic oxide particles and the surface of the carpet fibers. U.S. Pat. No. 2,881,146 (Remer), U.S. Pat. No. 3,916,053 (Sherman et al.), U.S. Pat. No. 3,940,359 (Chambers), U.S. Pat. No. 4,423,113 (Olive et al.), U.S. Pat. No. 4,600,735 (Larsson et al.) and U.S. Pat. No. 5,370,919 (Fieuws et al.) exemplify this technology.
Other attempts to improve the soil resistance of carpets have focused on the carpet manufacturing process itself. Both natural and synthetic carpet fibers contain oil residues on their surfaces at the time they are woven into the carpet. See, e.g., N. Nevrekar, B. Palan, "Spin Finishes for Synthetic Fibres--Part IV", Man-Made Textiles In India 331-336 (September 1991). These oil residues, which may be naturally occurring fats or waxes (in the case of wool and other natural fibers) or which may be residual spin finishes or other processing oils added during the manufacturing process (in the case of polypropylene and other synthetic fibers), significantly increase the tendency of the assembled carpet to attract dirt and other organic contaminants.
Consequently, it has become common practice in the art to "scour" carpets, a process which typically involves immersing the finished carpet in a bath of aqueous cleaning solution. The cleaning solution effectively reduces the amount of oil residue on the carpet to a level that does not significantly affect the soil resistance of the carpet. Indeed, it has long been considered essential that spin finishes be easily removable through scouring. See, P. Bajaj, R. Katre, "Spin Finishes", Colourage 17-26 (Nov. 16-30, 1987); W. Postman, "Spin Finishes Explained", Textile Research Journal, Vol. 50, No. 7 444-453 (July 1980).
One example of the use of scouring is illustrated in U.S. Pat. No. 3,592,684 (Smith) and U.S. Pat. No. 3,620,823 (Smith). There, carpet fibers are rendered soil resistant through treatment with a lubricating agent, silicone, and an inorganic oxide. The carpets are subsequently scoured to remove substantially all of the lubricating agent, while leaving behind a substantial portion of the silicone and inorganic oxide.
However, the immersion techniques involved in scouring carpets are undesirable in that they significantly increase the overall cost of manufacturing a carpet. After a carpet is scoured, it must be carefully dried in an oven or kiln to avoid warping or degradation of the carpet fibers. However, due to the immense effective surface area of a carpet, the carpet often absorbs many times its weight in water during scouring. Consequently, the drying process can be considerable, and consumes a significant amount of energy. This is especially true in the case of high quality carpets, which are usually denser than their lower quality counterparts. In the interim, the increased weight of the wetted carpets makes them very cumbersome to handle. Furthermore, to the extent that toxic solvents and chemicals are used or accumulate in the aqueous bath, the drying process generates a significant amount of air-borne and water-borne pollution. Scouring also frequently induces static problems in the treated carpet.
There is thus a need in the art for an alternative method to scouring that does not require significant drying procedures and times in the treated carpet, but that overcomes the adverse effect of residual oils on soil resistance. Such a method should avoid the dusting and pollution problems encountered with many prior art methods of carpet treatment, while rendering a carpet that has good soil resistance. These and other needs such as repellency of the treated carpet are met by the present invention, as hereinafter disclosed.